Re: [PATCH v3 5/7] perf report: Add latency output field

[Namhyung Kim <namhyung@kernel.org>]

On Wed, Jan 29, 2025 at 07:55:55AM +0100, Dmitry Vyukov wrote:
> On Wed, 29 Jan 2025 at 05:56, Namhyung Kim <namhyung@kernel.org> wrote:
> >
> > On Mon, Jan 27, 2025 at 10:58:52AM +0100, Dmitry Vyukov wrote:
> > > Latency output field is similar to overhead, but represents overhead for
> > > latency rather than CPU consumption. It's re-scaled from overhead by dividing
> > > weight by the current parallelism level at the time of the sample.
> > > It effectively models profiling with 1 sample taken per unit of wall-clock
> > > time rather than unit of CPU time.
> > >
> > > Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
> > > Cc: Namhyung Kim <namhyung@kernel.org>
> > > Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> > > Cc: Ian Rogers <irogers@google.com>
> > > Cc: linux-perf-users@vger.kernel.org
> > > Cc: linux-kernel@vger.kernel.org
> > > ---
> > >  tools/perf/ui/browsers/hists.c  | 27 ++++++++++------
> > >  tools/perf/ui/hist.c            | 29 ++++++++++-------
> > >  tools/perf/util/addr_location.h |  2 ++
> > >  tools/perf/util/event.c         |  6 ++++
> > >  tools/perf/util/events_stats.h  |  2 ++
> > >  tools/perf/util/hist.c          | 55 ++++++++++++++++++++++++---------
> > >  tools/perf/util/hist.h          | 12 +++++++
> > >  tools/perf/util/sort.c          |  2 ++
> > >  8 files changed, 100 insertions(+), 35 deletions(-)
> > >
> > > diff --git a/tools/perf/ui/browsers/hists.c b/tools/perf/ui/browsers/hists.c
> > > index 49ba82bf33918..35c10509b797f 100644
> > > --- a/tools/perf/ui/browsers/hists.c
> > > +++ b/tools/perf/ui/browsers/hists.c
> > > @@ -1226,7 +1226,7 @@ int __hpp__slsmg_color_printf(struct perf_hpp *hpp, const char *fmt, ...)
> > >       return ret;
> > >  }
> > >
> > > -#define __HPP_COLOR_PERCENT_FN(_type, _field)                                \
> > > +#define __HPP_COLOR_PERCENT_FN(_type, _field, _fmttype)                      \
> > >  static u64 __hpp_get_##_field(struct hist_entry *he)                 \
> > >  {                                                                    \
> > >       return he->stat._field;                                         \
> > > @@ -1238,10 +1238,10 @@ hist_browser__hpp_color_##_type(struct perf_hpp_fmt *fmt,             \
> > >                               struct hist_entry *he)                  \
> > >  {                                                                    \
> > >       return hpp__fmt(fmt, hpp, he, __hpp_get_##_field, " %*.2f%%",   \
> > > -                     __hpp__slsmg_color_printf, true);               \
> > > +                     __hpp__slsmg_color_printf, _fmttype);           \
> > >  }
> > >
> > > -#define __HPP_COLOR_ACC_PERCENT_FN(_type, _field)                    \
> > > +#define __HPP_COLOR_ACC_PERCENT_FN(_type, _field, _fmttype)          \
> > >  static u64 __hpp_get_acc_##_field(struct hist_entry *he)             \
> > >  {                                                                    \
> > >       return he->stat_acc->_field;                                    \
> > > @@ -1262,15 +1262,18 @@ hist_browser__hpp_color_##_type(struct perf_hpp_fmt *fmt,             \
> > >               return ret;                                             \
> > >       }                                                               \
> > >       return hpp__fmt(fmt, hpp, he, __hpp_get_acc_##_field,           \
> > > -                     " %*.2f%%", __hpp__slsmg_color_printf, true);   \
> > > +                     " %*.2f%%", __hpp__slsmg_color_printf,          \
> > > +                     _fmttype);                                      \
> > >  }
> > >
> > > -__HPP_COLOR_PERCENT_FN(overhead, period)
> > > -__HPP_COLOR_PERCENT_FN(overhead_sys, period_sys)
> > > -__HPP_COLOR_PERCENT_FN(overhead_us, period_us)
> > > -__HPP_COLOR_PERCENT_FN(overhead_guest_sys, period_guest_sys)
> > > -__HPP_COLOR_PERCENT_FN(overhead_guest_us, period_guest_us)
> > > -__HPP_COLOR_ACC_PERCENT_FN(overhead_acc, period)
> > > +__HPP_COLOR_PERCENT_FN(overhead, period, PERF_HPP_FMT_TYPE__PERCENT)
> > > +__HPP_COLOR_PERCENT_FN(latency, latency, PERF_HPP_FMT_TYPE__LATENCY)
> > > +__HPP_COLOR_PERCENT_FN(overhead_sys, period_sys, PERF_HPP_FMT_TYPE__PERCENT)
> > > +__HPP_COLOR_PERCENT_FN(overhead_us, period_us, PERF_HPP_FMT_TYPE__PERCENT)
> > > +__HPP_COLOR_PERCENT_FN(overhead_guest_sys, period_guest_sys, PERF_HPP_FMT_TYPE__PERCENT)
> > > +__HPP_COLOR_PERCENT_FN(overhead_guest_us, period_guest_us, PERF_HPP_FMT_TYPE__PERCENT)
> > > +__HPP_COLOR_ACC_PERCENT_FN(overhead_acc, period, PERF_HPP_FMT_TYPE__PERCENT)
> > > +__HPP_COLOR_ACC_PERCENT_FN(latency_acc, latency, PERF_HPP_FMT_TYPE__LATENCY)
> > >
> > >  #undef __HPP_COLOR_PERCENT_FN
> > >  #undef __HPP_COLOR_ACC_PERCENT_FN
> > > @@ -1279,6 +1282,8 @@ void hist_browser__init_hpp(void)
> > >  {
> > >       perf_hpp__format[PERF_HPP__OVERHEAD].color =
> > >                               hist_browser__hpp_color_overhead;
> > > +     perf_hpp__format[PERF_HPP__LATENCY].color =
> > > +                             hist_browser__hpp_color_latency;
> > >       perf_hpp__format[PERF_HPP__OVERHEAD_SYS].color =
> > >                               hist_browser__hpp_color_overhead_sys;
> > >       perf_hpp__format[PERF_HPP__OVERHEAD_US].color =
> > > @@ -1289,6 +1294,8 @@ void hist_browser__init_hpp(void)
> > >                               hist_browser__hpp_color_overhead_guest_us;
> > >       perf_hpp__format[PERF_HPP__OVERHEAD_ACC].color =
> > >                               hist_browser__hpp_color_overhead_acc;
> > > +     perf_hpp__format[PERF_HPP__LATENCY_ACC].color =
> > > +                             hist_browser__hpp_color_latency_acc;
> > >
> > >       res_sample_init();
> > >  }
> > > diff --git a/tools/perf/ui/hist.c b/tools/perf/ui/hist.c
> > > index 34fda1d5eccb4..22e31d835301e 100644
> > > --- a/tools/perf/ui/hist.c
> > > +++ b/tools/perf/ui/hist.c
> > > @@ -27,9 +27,10 @@ static int __hpp__fmt_print(struct perf_hpp *hpp, struct hists *hists, u64 val,
> > >                           int nr_samples, const char *fmt, int len,
> > >                           hpp_snprint_fn print_fn, enum perf_hpp_fmt_type fmtype)
> > >  {
> > > -     if (fmtype == PERF_HPP_FMT_TYPE__PERCENT) {
> > > +     if (fmtype == PERF_HPP_FMT_TYPE__PERCENT || fmtype == PERF_HPP_FMT_TYPE__LATENCY) {
> > >               double percent = 0.0;
> > > -             u64 total = hists__total_period(hists);
> > > +             u64 total = fmtype == PERF_HPP_FMT_TYPE__PERCENT ? hists__total_period(hists) :
> > > +                     hists__total_latency(hists);
> > >
> > >               if (total)
> > >                       percent = 100.0 * val / total;
> > > @@ -128,7 +129,7 @@ int hpp__fmt(struct perf_hpp_fmt *fmt, struct perf_hpp *hpp,
> > >                                 print_fn, fmtype);
> > >       }
> > >
> > > -     if (fmtype == PERF_HPP_FMT_TYPE__PERCENT)
> > > +     if (fmtype == PERF_HPP_FMT_TYPE__PERCENT || fmtype == PERF_HPP_FMT_TYPE__LATENCY)
> > >               len -= 2; /* 2 for a space and a % sign */
> > >       else
> > >               len -= 1;
> > > @@ -472,11 +473,13 @@ __HPP_ENTRY_AVERAGE_FN(_type, _field)                                   \
> > >  __HPP_SORT_AVERAGE_FN(_type, _field)
> > >
> > >  HPP_PERCENT_FNS(overhead, period)
> > > +HPP_PERCENT_FNS(latency, latency)
> > >  HPP_PERCENT_FNS(overhead_sys, period_sys)
> > >  HPP_PERCENT_FNS(overhead_us, period_us)
> > >  HPP_PERCENT_FNS(overhead_guest_sys, period_guest_sys)
> > >  HPP_PERCENT_FNS(overhead_guest_us, period_guest_us)
> > >  HPP_PERCENT_ACC_FNS(overhead_acc, period)
> > > +HPP_PERCENT_ACC_FNS(latency_acc, latency)
> > >
> > >  HPP_RAW_FNS(samples, nr_events)
> > >  HPP_RAW_FNS(period, period)
> > > @@ -548,11 +551,13 @@ static bool hpp__equal(struct perf_hpp_fmt *a, struct perf_hpp_fmt *b)
> > >
> > >  struct perf_hpp_fmt perf_hpp__format[] = {
> > >       HPP__COLOR_PRINT_FNS("Overhead", overhead, OVERHEAD),
> > > +     HPP__COLOR_PRINT_FNS("Latency", latency, LATENCY),
> > >       HPP__COLOR_PRINT_FNS("sys", overhead_sys, OVERHEAD_SYS),
> > >       HPP__COLOR_PRINT_FNS("usr", overhead_us, OVERHEAD_US),
> > >       HPP__COLOR_PRINT_FNS("guest sys", overhead_guest_sys, OVERHEAD_GUEST_SYS),
> > >       HPP__COLOR_PRINT_FNS("guest usr", overhead_guest_us, OVERHEAD_GUEST_US),
> > >       HPP__COLOR_ACC_PRINT_FNS("Children", overhead_acc, OVERHEAD_ACC),
> > > +     HPP__COLOR_ACC_PRINT_FNS("Latency", latency_acc, LATENCY_ACC),
> >
> > Hmm.. two latency fields have the same name.  Maybe better to
> > distinguish them but "Children Latency" or "Total Latency" would be
> > too long.. :(
> >
> > I think it's mostly ok since users will see them together with overhead
> > columns and it'll give the context ("Children" or "Self").  But it can
> > e called with -F or -s option to manually select those columns only.
> 
> Yes, the motivation for calling them the same was the column name length.
> 
> And, with the default flags it looks reasonable:
> 
>   Children  Latency      Self   Latency  Command
> 
> The fields seem to be selected based on the names in sort.c rather
> than these names, e.g. I can do:
> 
> perf report -F latency_children,overhead_children,latency,overhead,symbol
> 
> and get:
> 
> Samples: 45K of event 'cycles:Pu', Event count (approx.): 10457486861
>   Latency  Children   Latency  Overhead  Symbol
> +  19.35%    18.69%     0.00%     0.00%  [k] 0000000000000000
> +   4.86%     4.21%     4.86%     4.21%  [.] htab_find_slot_with_hash
> +   4.15%     4.48%     0.00%     0.00%  [.] 0xffffffff9ce012a6
> 
> So it seems to be possible to select these columns as needed.

Right, it's possible to use -F latency,latency_children,symbol and get:

  Samples: 45K of event 'cycles:Pu', Event count (approx.): 10457486861
    Latency  Latency  Symbol
  +   0.00%   19.35%  [k] 0000000000000000
  +   4.86%    4.86%  [.] htab_find_slot_with_hash
  +   0.00%    4.15%  [.] 0xffffffff9ce012a6

Thanks,
Namhyung